1. Field of the Invention
This invention relates to an apparatus for reproducing a signal from a magnetic recording medium such as a magnetic tape.
2. Description of the Related Art
Japanese published examined patent application 6-14723 discloses a method of tracking control in a home-use VTR (video tape recorder). In the method disclosed by Japanese application 6-14723, detection is made as to the presence and the absence of an audio FM signal reproduced via an audio head. In the presence of a reproduced audio FM signal, the tracking error of a rotary head assembly relative to a track on a magnetic tape is detected on the basis of the level of the reproduced audio FM signal. In the absence of a reproduced audio FM signal, the tracking error of the rotary head assembly is detected on the basis of the level of a video FM signal reproduced via a video head. Tracking control is implemented in response to the detected tracking error.
There are plural recording formats used by home-use VTR's. The plural recording formats include first, second, and third recording formats indicated hereafter.
According to the first recording format, an analog video signal is separated into a luminance signal (a Y signal) and a color signal (a C signal). The Y signal is converted by a frequency modulation (FM) process into an FM luminance signal in a frequency band of about 3.4 MHz to 4.4 MHz. The C signal is frequency-down-converted into a signal (a down-converted color signal) in a frequency band under the frequency band assigned to the Y signal. The FM luminance signal and the down-converted color signal are mixed with each other, and the resultant signal mixture is recorded on a magnetic tape via a group of rotary video heads. On the other hand, an audio signal is recorded via an audio head on a linear track extending along an edge of the magnetic tape.
The second recording format is a version extended from the first recording format. The second recording format prescribes audio-signal recording tracks in addition to a linear track. According to the second recording format, 2-channel analog audio signals are converted by frequency modulation (FM) processes into audio FM signals having carrier frequencies of 1.3 MHz and 1.7 MHz respectively. The audio FM signals are recorded on the magnetic tape via a group of rotary audio heads. The rotary audio heads have an azimuth angle considerably different from azimuth angles of the rotary video heads. The rotary audio heads positionally precede the rotary video heads. The rotary audio heads are designed to write the audio FM signals into a deep layer of the magnetic tape on which the rotary video heads can not act. Accordingly, the video signal and the two-channel audio signals are satisfactorily recorded on the magnetic tape.
The third recording format is a version extended from the second recording format. According to the third recording format, 2-channel analog audio signals can be replaced by digital information signals. Thus, digital information signals can be recorded instead of 2-channel analog audio signals.
Japanese published unexamined patent application 6-84107 discloses a video-signal reproducing system. The system of Japanese application 6-84107 includes an analog-signal reproducing head and a digital-signal reproducing head mounted on a same drum. The analog-signal reproducing head is successively followed by an analog-signal reproducing amplifier and an analog-signal processing circuit. The digital-signal reproducing head is successively followed by a digital-signal reproducing amplifier and a digital-signal processing circuit. In the system of Japanese application 6-84107, a sync detector connected to the analog-signal processing circuit decides whether an H-sync signal (or a V-sync signal) in a reproduced analog signal is present or absent. The decision by the sync detector is to detect whether a signal recorded in a magnetic tape is analog or digital. One of the reproduced analog signal and a reproduced digital signal is selected as a final output signal of the system in response to the result of the decision by the sync detector.
There is a known analog/digital VTR using the third recording format. The known analog/digital VTR is able to reproduce signals from a magnetic tape which have been recorded thereon according to any one of the first, second, and third recording formats.